Her work is supported by a five-year, $651,350 NSF CAREER grant.
With the temperature changes we experience in West Texas – from the bitterest cold winter days to the 100-plus-degree summers – most of us are acutely aware of the effects of temperature.
Many of us even recognize how temperature can affect our infrastructure. For example, we know concrete sidewalks and road surfaces expand when it's hot – that's why they're constructed with cracks or joints built in to allow for that movement. But in many materials, we don't yet know how temperature affects movement. And it's those materials that are of greatest interest to one Texas Tech University scientist.
Kristin Hutchins, an assistant professor in the Department of Chemistry & Biochemistry, has been awarded a five-year, $651,350 grant from the National Science Foundation's (NSF) Faculty Early Career Development Program (CAREER) to examine how molecules move in solid objects, how the bonds between molecules might affect temperature's impact and how molecules could be assembled to control thermal expansion behavior.
“There's a well-known remark by a chemist that says, ‘The crystal is a chemical graveyard,' because in a crystal or solid, the moleules can't do anything,” Hutchins said. “Molecules in a gas or a liquid can move really freely, but in a solid, people think they're locked in. What we and others have shown is, you can have motion in a solid. A lot of times it's not as big, maybe, as in a liquid or a gas, but solids can undergo motion. Now we're seeing that ability to undergo motion could actually affect a solid's properties.”
Hutchins and her lab members are studying temperature's effects on organic materials, like those in organic electronics.
“If you think about any material you use in the real world, it's often exposed to changes in temperature – that could be heating or cooling, depending on what the application is,” Hutchins said. “When you think about things like electronic components in a computer, they're typically exposed to heat, because things get hot when you have electricity running through them. When you design materials, you have to understand how they're going to respond when they're heated or cooled, so they don't break the first time the temperature changes.
“So, our research is trying to first understand then control how these materials respond.”
Materials with motion
The research's first aim is to examine groups of molecules that can undergo motion to see how temperature affects that motion.
Preliminary data has shown that when molecules in a material are undergoing motion, the material may expand as a result. Using that knowledge, Hutchins and her team hope to design materials that capitalize on molecules' motion, or lack thereof, for specific applications.
The problem is that, as of right now, what makes the molecules in some solids move and the molecules in others remain stationary is unclear.
“That motion, at this point in time, either happens or it doesn't – there's not a great way to say, ‘I want this to happen, so I'm going to do this,'” she explained. “You can put the right chemical structures in your material, and it might or it might not move. So, the goal is to really be able to say, ‘We want this to undergo motion and do this, so we're going to use these strategies to get that to happen.'”
All the studies done in Hutchins' lab are completed at variable temperatures. Many times, those temperatures are extremely cold, but the instrument also can raise the temperature above that of the surrounding room. Using that technique, one of Hutchins' students recently discovered the ability to turn motion on by heating up the crystal she was examining.
“So, then we begin to ask what we can do with regard to temperature,” Hutchins said. “Can we control being able to turn the motion on at a higher temperature, and then turn it off when we cool it down?
“For me, that's just fun. People don't necessarily think motion can happen when it's a solid, but on that molecular level, something is happening."
Reversible reactions
The research's second aim is another new concept Hutchins is excited about. Her team will essentially take two molecules near one another, connect them to each other and see how that connection affects their expansion capability.
“We have one preliminary study showing that when we connected the molecules, we made the expansion go down, because we're using stronger forces to hold them together and, so, it's less affected by temperature,” Hutchins explained. “We're trying to study reactions that can make the bonds and then limit the expansion.”
In theory, such reactions should be reversible – that is, researchers should be able to connect the molecules to limit their expansion, and break them apart to regain their initial qualities. As such, testing that theory is yet another aspect of the work.
Going 3D
The research's third aim is to improve how organic materials can be constructed in 3D. As Hutchins explains, the molecules in metals are able to coordinate an exact number of times – for simplicity's sake, imagine one molecule can connect to six others: one in front, back, right, left, up and down. Because they coordinate so well, scientists can easily control how metals form a 3D structure.
Organic materials don't coordinate in the same way, and certainly not as well. As such, it's much more difficult for chemists to control how organic materials are assembled in three dimensions – not to mention how that assembly changes when temperature does. Thus, the goal of this part of the research is to test different types of interactions between molecules to see how each behaves. Eventually, Hutchins hopes to create a toolbox of sorts for future chemists.
“When you talk about concrete and products that are used widely, we know how these materials respond to temperature because they have been in existence for a long time,” Hutchins said. “Even for materials that are based on metals, people can look at it and say, ‘OK, this is how the structure should respond, because it's held together so predictably.' But with organics, it's difficult to control the structure. If you can't do that, it's difficult to predict what's going to happen, because you could get a different structure just by making small structural changes.
“We'd like to be able to say definitively, ‘OK, if I use this interaction, this is the expansion behavior I'm going to get.' Then, you know you can use this one to get a large expansion or that one to get a small expansion, depending on your application.”
Hutchins compares it to Legos. If you know that red Legos can connect end-to-end to blue Legos, it's fairly simple to create a long chain of alternating red and blue Legos. Once you begin bonding other chains side-by-side with that chain, translating into two dimensions, it becomes more complicated. Perhaps red Legos can't connect sideways, but yellow or green Legos can. By the time you begin to stack Legos, moving into three dimensions, it becomes more complex than we're currently capable of dealing with.
“Our goal would be, one, to control 3D structure, and two, to really show and understand how, if you use certain interactions, what are the properties of the material going to be?” Hutchins said. “Really, we don't know that in the organic solid state field.
“If I use this blue and red pair of Legos, what happens to that interaction when I change the temperature? Maybe if we use blue and red, it holds really strongly, but if I use blue and yellow, it changes a lot. With organics, you can pair all different types of molecular Legos, for example, blue and yellow, blue and red, or blue and green. What if you have blue, red and yellow present in your structure? You might have a situation where there are many options for what could pair up with each other.”
The goal, she emphasized, is to fine tune our understanding of the interactions so that, one day, we can select the appropriate interaction for the outcome we want.
Advancing education
As with any CAREER grant, a significant part of Hutchins' project relates to education. While some faculty members choose to bring students into their labs, Hutchins has opted to take the lab to the students. She has designed activities appropriate for middle schoolers, high schoolers, undergraduates and even graduate students and now is partnering with other entities across campus to bring scientific opportunities to those students where they are.
The STEM Center for Outreach, Research & Education (STEM CORE) hosts an annual one-day science, technology, engineering and mathematics conference for sixth- through eighth-grade girls and their parents. Called Tech Savvy, the conference offers a variety of workshops designed to help young girls discover realistic STEM careers and pathways to education. In collaboration with STEM CORE, Hutchins will add information on the real-world applicability of thermal expansion into Tech Savvy's existing chemistry workshop.
The Center for the Integration of STEM Education & Research (CISER) offers traveling labs – fully equipped and supplied STEM activities they pack into a trunk and ship off to schools across the state. Working with CISER, Hutchins will design an experiment on how solid-state structures are made and the properties of solid materials, with an emphasis on thermal expansion. Then, CISER will facilitate sending that experiment to high school teachers throughout Texas so they can share it with their classes.
In talking to undergraduate and graduate students in the Department of Chemistry & Biochemistry over the last few years, Hutchins realized one shortcoming in career preparation for these students – most of the people offering them career advice chose careers in academia, not industry. So, she's using this project to address those needs as well, by offering a workshop on applying for non-academic jobs.
“Most faculty went the all-academic route, and that's the career route we know, so that's what we can offer advice on, but not everybody goes that route,” Hutchins said. “So, the idea is to have a workshop that would help with prepping a resume, interview skills, networking and, then, have somebody who's in industry currently offer some advice to the students on that.”
Looking ahead
For someone who spends so much of her time studying microscopic details, such a long-term, all-encompassing project might seem quite overwhelming.
“I try to see things in smaller pieces, like what are we doing today or this week, rather than ‘OK, what do the next five years look like?'” Hutchins laughed. “Today, I'm seeing the whole big picture of everything, and it's like, wow. But, from the day-to-day perspective, we can focus on what we are doing right now and what data we need for this specific study to wrap up.”
She says it helps that she has such an outstanding group of student researchers, each handling their own portion of the project.
“Our group dynamic is really good,” she said. “Everybody's excited and motivated, and that always makes it more fun.”
It's especially enjoyable because the challenges of their work are fun challenges, Hutchins emphasized.
“If you just look at a solid, you can't really tell motion's happening, because it's on the molecular and structural level,” she said. “But, for me, that's fun – the idea that something you might not be able to see with your naked eye is actually happening on such a small level, and it can affect the properties of the whole material.
“In graduate school, when I would solve a crystal structure, it was always kind of like a puzzle. It is fun to solve it.”
